Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Hydraulic pressure control valve with pneumatic actuation
Technical Field
The present invention relates to a hydraulic pressure control valve with
pneumatic actuation.
Background
Mobile working machines, such as trucks, excavators or wheel loaders, may have
moveable
parts that are attached or attachable to the respective machine and whose
movement is
achieved by means of a hydraulic cylinder or hydraulic motor. Pressurized
hydraulic liquid may
be provided by a hydraulic pump. Flow of hydraulic liquid to the hydraulic
cylinder or hydraulic
motor is typically controlled by one or more directional control valves, which
direct the flow of
hydraulic liquid to and from the hydraulic cylinder or hydraulic motor.
Summary
A hydraulic pressure control valve with pneumatic actuation according to the
independent
claims ist proposed. Advantageous embodiments form the subject matter of the
dependent
claims and of the subsequent description.
The hydraulic pressure control valve comprises a valve body, a spool, and a
sealing element.
The spool is installed (i.e. located or disposed) in a bore (first channel) of
the valve body and
is movable between a first end position and a second end position. The spool
has lands, such
that in the first end position a first port and a third port are connected and
in the second end
position the first port and a second port are connected. The spool has a first
end and a second
end in axial direction, wherein a first face of the spool near the first end
is connected to a first
control port (which is configured to receive hydraulic fluid). The sealing
element is arranged
between a second control port (which is configured to receive hydraulic gas)
and the first bore
to seal the second control port from the first bore, further, the sealing
element is flexible, such
that movement of a part of the sealing element in axial direction is possible,
and is coupled to
the second end, such that the sealing element is able to exert force onto the
spool that effects
movement of the spool in direction of the second end position. By using a
flexible sealing
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Date Recue/Date Received 2022-12-20
element, such as a membrane, firstly, separation of the parts of the valve, in
which hydraulic
fluid (e.g. hydraulic oil) is present, from parts of the valve, in which
pneumatic gas (e.g. air) is
present, is achieved. Secondly, force due to the pneumatic pressure is used to
cause move-
ment of the spool, such that the flow of hydraulic fluid through the pressure
control valve is
controlled by the pressure of the pneumatic gas received at the second control
port.
As used herein (unless otherwise stated or apparent from the context), the
term "connected"
means connected for fluid exchange, i.e. a fluid (such as hydraulic fluid or
pneumatic gas) may
flow between elements (e.g. ports) that are connected.
Further advantages and embodiments of the invention will become apparent from
the descrip-
tion and the appended figures.
The invention is shown schematically in the figures on the basis of exemplary
embodiments
and will be described in the following, with reference to the figures.
Short Description of the Figures
Figure 1 shows a hydraulic pressure control valve with pneumatic actuation
according to an
embodiment.
Figure 2 schematically shows an exemplary system which uses a hydraulic
pressure control
valve as shown in Figure 1.
Detailed Description
Figure 1 shows a hydraulic pressure control valve 2 with pneumatic actuation
according to an
embodiment. The pressure control valve 2 includes a valve body 4, a spool 6,
and a sealing
element 8.
In the shown exemplary embodiment, the valve body 4 has three valve body parts
41, 42, 43.
For example, without limitation, the first valve body part 41 and the second
valve body part 42
are connected by a press fitting, and the second valve body part 42 and the
third valve body
part 43 are connected by a threaded fitting. Other numbers of valve body parts
and methods
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Date Recue/Date Received 2022-12-20
of connections are possible as well. Sealing rings (0-rings) may be used to
seal the connec-
tions between the valve body parts.
The valve body 4 has a first port A, a second port P, and a third port T,
which serve as in-
let/outlet ports for hydraulic fluid. The valve body 4 has a first control
port X1 (first sensing port)
for receiving a hydraulic fluid and a second control port X2 (second actuation
port / second
sensing port) for receiving a pneumatic gas (e.g. air). The first, second, and
third ports A, P, T
as well as the first control port X1 are provided in the first valve body part
41, for example. The
second control port X2 is provided in the third valve body part 43, for
example.
The valve body 4 includes an internal first bore 10 (or first channel)
extending in axial direction,
in which the spool 6 is supported. The first bore 10 extends through the first
and second valve
body parts, for example. The first bore 10 and the spool 6 extend in an axial
direction of the
valve body 4. The first port A, the second port P, and the third port T are
connected to the first
bore 10 by channels extending in essentially radial direction.
The spool 6 is movable in the first bore 10 in the axial direction between a
first end position (
the position shown in the figure) and a second end position. The spool 6 has
circumferential
lands. In the first end position the first and third ports A, T are connected
by means of these
lands and the associated spool position (i.e. by means of the circumferential
groove between
these lands). In the second end position the first and second ports A, P are
connected by
means of these lands and the associated spool position. That is, in the first
end position flow
of hydraulic fluid is possible between the first and third ports A, T, and in
the second end
position flow of hydraulic liquid is possible between the first and second
ports A, P. In the first
end position the first and second ports A, P are not connected by means of the
lands (i.e. no
flow of hydraulic fluid is possible between the first and second ports A, P in
the first end posi-
tion, except for leakage). In the second end position the first and third
ports A, T are not con-
nected by means of the lands (i.e. no flow of hydraulic fluid is possible
between the first and
third ports A, T in the second end position, except for leakage).
In the shown embodiment the length of the lands and the distance of the second
and third
ports P, T from each other (length and distance in axial direction), i.e. the
positioning of control
edges (control notches), is such that the second and third ports P, T may not
be connected to
the first port A simultaneously. That is, the second and third ports P, T may
not be connected
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Date Recue/Date Received 2022-12-20
by the lands. It will be appreciated by those skilled in the art that in other
embodiments (not
shown) the length of the groove and the distance of the second and third ports
P, T from each
other, i.e. the positioning of control edges, may be arranged, such that in an
intermediate po-
sition of the spool the second and third ports P, T are connected to the first
port A simultane-
ously (i.e. the second and third ports P, T may be connected by the lands).
The spool 6 is biased into the first end position by a biasing element, for
example a spring 12.
In axial direction, the spool 6 has a first end 18 (first axial end) and a
second end 20 (second
axial end). The second end 20 is opposite to the first end 18 in an axial
direction. A first face
22 of the spool 6 that is near the first end 18 is connected to the first
control port X1. The first
face 22 is perpendicular to the axial direction and is arranged to receive
pressure of hydraulic
fluid received at the first control port X1 (or a receiving chamber thereof).
Pressure exerted
onto the first face 22 causes a force to move the spool 6 into the direction
of the first end
position.
The sealing element 8 is flexible such that movement of a part of the sealing
element 8 in axial
direction is possible. The sealing element 8 may be elastic or resilient, for
example. The sealing
element 8 is arranged to isolate (sealingly separate) the second control port
X2 (or a receiving
chamber thereof) from the first valve bore 10, such that fluid exchange (i.e.
liquid exchange
and gas exchange) is prevented between the second control port and the first
bore. The seal-
ing element 8 is further coupled to the second end 20. The coupling to the
second end 20 is
such that the sealing element is able to exert force onto the spool that
effects a movement of
the spool in direction of the second end position. On the other hand, the
coupling to the second
end 20 may be such that the sealing element is not able to exert force onto
the spool that
effects a movement of the spool in direction of the first end position (as
shown). The coupling
of the sealing element 8 to the second end 20 may be direct or indirect. In a
direct coupling,
the sealing element 8 to the second end 20 are in contact to achieve the
coupling. In an indirect
coupling (as shown), the sealing element 8 to the second end 20 are coupled by
means of a
coupling member 24. For example, the sealing element 8 may be coupled to the
second end
20 such that the sealing element itself (direct coupling) or the coupling
member 24 (indirect
coupling) abuts a second (axial) face 26 of the spool near the second end 20.
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Date Recue/Date Received 2022-12-20
The shown sealing element 8 is, for example, a membrane having a disc shape.
As shown,
the sealing element 8 may be (press) fitted between the second and third valve
body parts 42,
43. A first surface 14 of the membrane is configured to receive pressure from
the gas, i.e. the
first surface forms a barrier (or wall) of the second control port X2 (or a
receiving chamber
thereof), such that the pneumatic pressure received at the second control port
X2 acts onto
the first surface 14. A second surface 16 of the membrane 8, which is opposite
to the first
surface 14, is coupled to the second end 20 by means of the coupling member
24.
The coupling member 24 may have a radial protrusion 28 which extends into a
recess 30
formed in the valve body. The recess is formed as recess in the first valve
body part 41, for
example. The axial lengths of the protrusion 28 and the recess 30 are
configured such that the
movement of the coupling member 24 and/or of the spool 6 in axial direction is
restricted. This
defines the first and the second end positions of the spool 6 as explained
above. It will be
appreciated by those skilled in the art that other configurations are possible
to achieve a re-
striction of the movement of the coupling member 24 and/or of the spool 6 in
axial direction or
at least in one of the two (left/right in the figure) possible axial movement
directions. For ex-
ample, a protrusion may be provided on the spool.
In another example, not shown, the sealing element may have the shape of a
(flat) ring, e.g. a
membrane having an opening in the middle. In this case the coupling to the
second end could
be achieved by extending the second end or the coupling element through the
opening and
fixing, e.g. moulding, the second end or the coupling element to a
circumference of the open-
ing.
According to an embodiment the valve body may include a second (internal) bore
or second
channel (not shown) that extends in axial direction and connects the first
port A with the first
control port X1. In this way the pressure of hydraulic liquid at the first
port A acts as control
pressure at the first control port X1 onto the first face 22.
It will be appreciated by those skilled in the art that in typical use
scenario the directional control
valve 22 (as shown) may be mounted to a housing (not shown), e.g. by means of
threads
provided on the valve body 4 (such as on the second valve body part 42). The
housing, e.g. a
housing body thereof, includes channels to connect the ports and control ports
of the direc-
tional control valve to respective ports provided on the outer surface of the
housing body. In
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Date Recue/Date Received 2022-12-20
case the pressure control valve has no second bore that connects the first
port and the first
control port, such a channel may be provided in the housing body, if required.
It will further be appreciated by those skilled in the art that Figure 1 is
merely a non-limiting
example presented for illustrative and explanatory purposes.
Figure 2 schematically shows a non-limiting exemplary system 50 that includes
a pressure
control valve 2 such as shown in Figure 1.
The system includes a source for pressurized air 52, e.g. an air tank or
compressor. The air
source 52 is connected to a pneumatic control unit 54 by a pneumatic line. The
pneumatic
control unit 54 may include a pneumatic control valve (not shown) which
controls the flow of
pressurized air from the air source 52 to a pneumatic control line 56
connected to the second
control port X2 of the pressure control valve 2. The pneumatic control unit 54
and in particular
its pneumatic control valve may be actuated by a user by means of a hand
lever, for example.
Other actuation mechanism may be used as well, such as electric and/or electro-
magnetic
actuation, allowing control by an electronic controller.
The second port P (pump port) of the pressure control valve 2 is hydraulically
connected to a
hydraulic pump 58 by a hydraulic line. The pump 58 is configured to pump
hydraulic fluid (such
as a hydraulic oil) from a tank 60 into the hydraulic line (and via this
hydraulic line to the second
port P),. The third port T (tank port) of the directional control valve 2 is
hydraulically connected
to the tank 60 for hydraulic liquid.
The first port A (working port) of the directional control valve 2 is
hydraulically connected to a
hydraulic load, such as a hydraulic cylinder 62, a hydraulic motor (not
shown), a hydraulically
actuated valve (not shown) etc., by means of a hydraulic line. Especially, the
pressure control
valve 2 can be used as a pilot valve for a hydraulically actuated valve.
The first port A is further connected to the first control port X1 of the
directional control valve 2
by a hydraulic control line 64, which may be implemented internally in the
directional control
valve 2 by the second bore (or channel). By this, the pressure on port A is
sensed (or con-
trolled) by the pressure on port X2.
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Date Recue/Date Received 2022-12-20
In the state as shown, the spool of the directional control valve 2 is in the
first position, such
that the first port A is hydraulically connected to the third port T, i.e.
flow of hydraulic liquid form
the hydraulic cylinder 62 to the tank 60 is possible, while no flow of
hydraulic liquid from the
pump 58 to the hydraulic cylinder 62 is possible. The directional control
valve 2 is biased into
the first position by spring 12.
By operating the pneumatic control unit 54 accordingly, flow of pressurized
air from the air
source 52 into the pneumatic control line 56 may be enabled, such that the
pneumatic pressure
at the second control port X2 increases and causes the spool 6 of the
directional control valve
.. 2 to move into the second position once the biasing force of spring 12 is
overcome. In turn
hydraulic fluid flows from the hydraulic pump 60 to the first port A and from
there to the hy-
draulic cylinder 62. The pressure of hydraulic fluid at the first port A and
therefore in the hy-
draulic control line 64 and at the first control port X1 increases until an
equilibrium between,
on one side, the (pneumatic) force exerted by the air at the second control
port X2 and, on the
other side, the sum of the forces exerted by the spring 12 and by the
hydraulic liquid at the first
control port X1 is reached. By regulating (or controlling) the pneumatic
control unit 54 accord-
ingly, the pressure of the air in the pneumatic control line 56 and therefore
at the second control
port X2 may be controlled. Thus, the pressure of the hydraulic fluid at the
first port A supplied
to the hydraulic cylinder 62 may be regulated by controlling the pneumatic
control unit 54. For
example, the pressure of the hydraulic liquid at the first port A may increase
essentially linearly
with the pressure of the air at the second control port X2.
It will be appreciated by those skilled in the art that in systems other than
the system shown in
Figure 2, the ports of the directional control valve 2 may be connected
differently to a hydraulic
pump, a hydraulic load, a hydraulic tank, and/or a pneumatic control unit.
It will also be appreciated by those skilled in the art that the disclosure
has been illustrated by
describing one or more specific examples thereof, but is not limited to these
examples; many
variations and modifications are possible, within the scope of the
accompanying claims.
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Date Recue/Date Received 2022-12-20
